320 M. H. RICHARDS AND RAY M. BALYEAT 



Matings between allergic families also establish this point. In family 8, 

 migraine had appeared for two generations on both sides and no other 

 allergy had been manifest. The father and mother, both free from allergy, 

 had seven children, two of whom suffered from migraine, and another from 

 five allergies, namely, migraine, eczema, asthma, urticaria, and hay fever. 

 How was it possible for four allergies, apparently new to both sides of the 

 family (three of which have been shown in our other crosses with negative 

 lines to be dominants) to be present for two generations without manifesting 

 themselves? 



Other matings of two individuals, both from allergic families, also produce 

 children with allergies which have not appeared in either family. Thus in 

 families 2, 20, and 13 urticaria appears as a new allergy; in family 11 mi- 

 graine; in family 17 eczema; in family 31 hay fever. In this last case, as in 

 the cases with negative lines, two allergies present in the family did not 

 appear in any of the progeny. One parent had asthma and a grandparent 

 had bronchitis, neither of which reappeared in the children. 



These facts all lend support to the theory that there is only one gene for 

 sensitivity and that this gene expresses itself in various ways in different 

 individuals. This point, we believe, is definitely established by our crosses 

 with negative lines. 



In reviewing our charts, it is at once evident that migraine is more prev- 

 alent in females than in males. Among our pedigrees we find 64 males 

 with migraine and 126 females so affected. At first sight, it might seem 

 that migraine has something to do with the sex chromosome, for if it were 

 dominant, as we have shown, but also sex linked, we should expect more 

 migraine females than males. Our records show, however, that a son may 

 inherit migraine from either his father or his mother. He may have mi- 

 graine if his mother is from a negative family (family 41) and his father has 

 migraine; or if his father is from a negative family and his mother has 

 migraine (family 5). Apparently a son may be allergic if his parents are 

 from allergic lines, regardless of which parent has migraine, or even if neither 

 has that special form of allergy. The following chart makes this matter 

 clear. In these cases both father and mother are most probably from 

 allergic families. (See table 2.) 



Since our records show that with the same inheritance females are more 

 likely to have this allergy than males, the reason for this difference must 

 probably be sought in the physiological differences between the sexes. One 

 might conjecture that the more highly organized nervous system of the 

 female, or the hormones related to sex may be the cause of the different 

 proportions. 



The conclusions of this paper are in harmony with the work of most other 



